Magnetoresistive effect element, magnetic memory and magnetic head

ABSTRACT

A magnetoresistive effect element of a tunnel junction type includes a magnetic multi-layered film ( 1 ), ferromagnetic film ( 3 ) and intervening insulating film ( 2 ) such that a current flows between the magnetic multi-layered film and the ferromagnetic film, tunneling through the insulating film. The magnetic multi-layered film includes a first ferromagnetic layer, second ferromagnetic layer and anti-ferromagnetic layer inserted between the first and second ferromagnetic layers.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2001-298849, filed onSep. 28, 2001; the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] This invention relates to a magnetoresistive effect element,magnetic memory and magnetic head, and more particularly to those havinga ferromagnetic tunnel junction structure and capable of maintaininghigh sensitivity to an external magnetic field even when miniaturized indevice size.

[0003] Magnetoresistive effect elements are under expectation towardpractical use in a wide field of application including magnetic detectorelements such as magnetic heads, magnetic memory devices, etc.

[0004] For example, there is a proposal of magnetic random access memoryusing a magnetic element exhibiting giant magnetoresistance effect as asolid magnetic storage device. Especially, magnetic memory using“ferromagnetic tunnel junction” is remarked as a magnetic element.

[0005] Ferromagnetic tunnel junction is mainly made of a three-layeredfilm of first ferromagnetic layer/insulating film/second ferromagneticlayer, and a current flows, tunneling through the insulating film. Inthis case, the junction resistance value varies proportionally to thecosine of the relative angle between magnetization directions of thefirst and second ferromagnetic layers. Therefore, resistance valuebecomes minimum when the magnetization directions of the first andsecond ferromagnetic layers are parallel, and becomes maximum when theyare anti-parallel. This is called tunneling magnetic resistance (TMR)effect. For example, in the literature, Appl. Phys. Lett., Vol. 77, p283(2000), it is reported that changes of resistance value by TMR effectreaches as high as 49.7% at the room temperature.

[0006] In a magnetic memory including a ferromagnetic tunnel junction asa memory cell, magnetization of one of ferromagnetic layers is fixed asa “reference layer”, and the other ferromagnetic layer is used as a“recording layer”. In this cell, by assigning parallel and anti-parallelmagnetic orientations of the reference layer and the recording layer tobinary information “0”, and “1”, information can be stored.

[0007] For writing information, magnetization of the recording layer isreversed by a magnetic field generated by supplying a current to a writeline provided for the cell, and by detecting a resistance change by TMReffect. A number of such memory elements are aligned to form alarge-capacity memory device.

[0008] Its actual configuration is made up by placing a switchingtransistor for each cell and combining peripheral circuits similarly toDRAM (dynamic random access memory), for example. There is also aproposal of a system incorporating ferromagnetic tunnel junctions incombination with diodes at crossing positions of word lines and bitlines (U.S. Pat. No. 5,640,343 and U.S. Pat. No. 5,650,958).

[0009] For higher integration of magnetic memory elements usingferromagnetic tunnel junctions as memory cells, the size of each memorycell becomes smaller, and the size of the ferromagnetic element formingthe cell inevitably becomes smaller. There is the same situation inmagnetic recording systems when the recording density is enhanced andthe recording bit size is decreased.

[0010] In general, as the ferromagnetic element becomes smaller, itscoercive force increases. Since the intensity of the coercive forcegives criteria for judging the magnitude of the switching magnetic fieldrequired for reversal of magnetization, its increase directly means anincrease of the switching magnetic field. Therefore, upon writing bitinformation, a larger current must be supplied to the write line, and itinvites undesirable results such as an increase of power consumption,shortening the wiring lifetime, etc. Therefore, it is an important issuefor practical application of high-integrated magnetic memory to reducethe coercive force of the ferromagnetic element used as the memory cellof magnetic memory.

[0011] To overcome this problem, it has been proposed to use, as a“recording layer”, a structure including multi-layered film of at leasttwo ferromagnetic layers and a nonmagnetic layer interposed between themand including anti-ferromagnetic coupling between those ferromagneticlayers (Japanese Patent Laid-Open Publication No. H9-25162, JapanesePatent Application No. H11-263741 and U.S. Pat. No. 5,953,248).

[0012] In this case, two ferromagnetic layers included in the “recordinglayer” are different in magnetic moment and thickness, and theirmagnetic orientations are opposite under anti-ferromagnetic coupling.Therefore, they effectively cancel each other's magnetization, and theentirety of the recording layer can be regarded equivalent to aferromagnetic element having small magnetization in the easy axisdirection. If a magnetic field is applied in the opposite direction fromorientation of the small magnetization in the easy axis direction therecording layer has, magnetization of each ferromagnetic layer reverseswhile holding the anti-ferromagnetic coupling. Therefore, because of theclosed magnetic line of force, influences of the demagnetizing field aresmall, and the switching magnetic field of the recording layer isdetermined by the coercive force of each ferromagnetic layer. As aresult, even a small switching magnetic field enables magnetic reversal.

[0013] In case that no layer-to-layer coupling exists between themagnetic layers (J=0), there is an interaction by magnetostatic couplingby the leak magnetic field from the magnetic layers. In this case,however, it is known that the switching magnetic field decreasessimilarly to a case where such coupling exists (24th Japan AppliedMagnetics Academy Scientific Lecture 12aB-3, 12aB-7, 24th Japan AppliedMagnetics Academy Scientific Lecture Summary p.26, 27).

[0014] However, in case that only magnetostatic coupling exists withoutno layer-to-layer coupling between magnetic layers, the magneticstructure made by the above-explained magnetization is unstable.Additionally, the squareness in the hysteresis curve or themagnetoresistance curve is small, and it is difficult to obtain a largemagnetoresistance ratio. Therefore, it is not preferable for use as amagnetoresistive.

[0015] As explained above, reducing the switching magnetic fieldnecessary for magnetic reversal of the “recording layer” is anindispensable factor for realization of a high-density magneticrecording system or magnetic memory, and it has been proposed to use amulti-layered film including anti-ferromagnetic coupling through anonmagnetic metal layer.

[0016] However, as already recognized, in a minute ferromagnetic elementin a minute magnetoresistive effect element as used in a high-densitymagnetic recording system or high-integrated magnetic memory, when thewidth of its shorter axis is miniaturized to the level of severalmicrons through sub microns, a magnetic structure different from acentral portion of the magnetic element is generated in perimeterportions of the magnetized region due to influences of an “demagnetizingfield”. Such a magnetic structure in perimeters is called “edge domain”(see, for example, J. App. Phys., 81, p.5471(1977)).

[0017]FIGS. 18A and 18B are schematic diagrams showing magneticstructures having such edge domains, respectively. In any of themagnetic structures shown in FIGS. 18A and 18B, magnetization M1 isgenerated in a direction in accordance with the magnetic anisotropy in acentral portion of the magnetized region. In opposite end portions,however, magnetizations M2 through M5 are generated in directionsdifferent from that of the central portion. In this explanation, thedomain structure shown in FIG. 18A is called “S-type structure”, and thedomain structure shown in FIG. 18B is called “C-type structure”.

[0018] In a minute magnetic element used in a high-density magneticrecording system or high-integrated magnetic memory, the edge domaingenerated in its end portions exert strong influences, and changes ofthe magnetic structure pattern upon magnetic reversal becomescomplicate. As a result, the coercive force increases, and the switchingmagnetic field undesirably increases.

[0019] As a method for minimizing such complicate changes of themagnetic structure, there is a proposal to fix the edge domain (U.S.Pat. No. 5,748,524, Japanese Patent Laid-Open 2000-100153). This methodcan certainly control behaviors upon magnetic reversal, but cannotsubstantially reduce the switching magnetic field. Additionally, hismethod needs an additional structure for fixing the edge domain, and itis not suitable for higher-density applications.

SUMMARY OF THE INVENITON

[0020] In some embodiments of the invention, as the ferromagnetic layerused as a magnetically free layer or a recording layer of amegnetoresistive element of a ferromagnetic tunnel junction type, amulti-layered film including a ferromagnetic layer and ananti-ferromagnetic layer is used. Thus a magnetoresistive effect elementis provided, in which the switching magnetic field is reduced by makinginteraction by exchange coupling (or magnetostatic coupling) between theantiferromagnetic layer and the ferromagnetic layer, which is adjacentto the anti-ferromagnetic layer or placed nearest thereto via anonmagnetic metal layer (or dielectric layer).

[0021] Exemplary structures of this kind of magnetic multi-layered filmare: ferromagnetic layer/anti-ferromagnetic layer/ferromagnetic layer;ferromagnetic layer/nonmagnetic metal layer/anti-ferromagneticlayer/nonmagnetic metal layer/ferromagnetic layer; and ferromagneticlayer/dielectric layer/anti-ferromagnetic layer/dielectriclayer/ferromagnetic layer. In case of the structure of ferromagneticlayer/anti-ferromagnetic layer/ferromagnetic layer, a weakanti-ferromagnetic material is preferably used to control the magnitudeof exchange coupling between the anti-ferromagnetic layer and theferromagnetic layer.

[0022] In case of the structure of ferromagnetic layer/nonmagnetic metallayer/anti-ferromagnetic layer/nonmagnetic metal layer/ferromagneticlayer, exchange coupling can be controlled by adequately determining thematerial and thickness of the nonmagnetic metal layer placed between theanti-ferromagnetic layer and the ferromagnetic layer.

[0023] Similarly, in case of the structure of ferromagneticlayer/dielectric layer/anti-ferromagnetic layer/dielectriclayer/ferromagnetic layer, exchange coupling can be controlled byadequately determining the material and thickness of the dielectriclayer placed between the anti-ferromagnetic layer and the ferromagneticlayer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be understood more fully from thedetailed description given herebelow and from the accompanying drawingsof the embodiments of the invention. However, the drawings are notintended to imply limitation of the invention to a specific embodiment,but are for explanation and understanding only.

[0025] In the drawings:

[0026]FIG. 1 is a schematic diagram illustrating a cross-sectionalstructure of the substantial part of a magnetoresistive effect elementaccording to the first embodiment of the invention;

[0027]FIG. 2 is a schematic diagram of a multi-layered structure of amagnetic multi-layered film 1;

[0028]FIG. 3 is a graph diagram showing magnetic hysteresis of themagnetic multi-layered film 1 shown in FIG. 2;

[0029]FIG. 4 is a graph diagram showing magnetic hysteresis of a simplexferromagnetic layer taken as a comparative example;

[0030]FIG. 5 is a graph diagram showing a relation between the exchangecoupling intensity Hex and the coercive force Hc;

[0031]FIG. 6A is a schematic diagram showing a domain pattern appearingin ferromagnetic layers 1A, 1C under exchange coupling of the magnitudeHc as large as 30 0e;

[0032]FIG. 6B is a schematic diagram showing a domain pattern in asimplex ferromagnetic layer as a comparative example;

[0033]FIG. 7 is a schematic diagram showing a cross-sectional structureof the substantial part of a magnetoresistive effect element accordingto the second embodiment of the invention;

[0034]FIG. 8A is a graph diagram showing magnetization and hysteresis ofa multi-layered structure according to the second embodiment;

[0035]FIG. 8B is a graph diagram showing magnetization and hysteresis ina simplex ferromagnetic layer taken as a comparative example;

[0036]FIG. 9 is a graph diagram plotting values of coercive force inrelation to reciprocals of the width of the ferromagnetic layers 1A, 1C;

[0037]FIG. 10 is a diagram showing a cross-sectional structure of thesubstantial part of a magnetoresistive effect element taken as the thirdspecific example of the invention;

[0038]FIG. 11A is a diagram showing a cross-sectional structure of thesubstantial part of a magnetoresistive effect element taken as thefourth specific example of the invention;

[0039]FIG. 11B is a diagram showing a cross-sectional structure of thesubstantial part of a magnetoresistive effect element taken as the fifthspecific example of the invention;

[0040]FIG. 12 is a schematic diagram illustrating configuration of thesubstantial part of a MRAM according to an embodiment of the invention;

[0041]FIG. 13 is a cross-sectional view showing another specific exampleof MRAM cell according to an embodiment of the invention;

[0042]FIG. 14 is a diagram schematically showing configuration of thesubstantial part of a magnetic head according to an embodiment of theinvention;

[0043]FIG. 15 is a diagram schematically showing configuration of thesubstantial part of a magnetic head according to an embodiment of theinvention;

[0044]FIG. 16 is a perspective view of general configuration of thesubstantial part of a magnetic record/reproduce apparatus using amagnetoresistive effect element according to an embodiment of theinvention;

[0045]FIG. 17 is an enlarged, perspective view of a distal end from anactuator arm 155 of a magnetic head assembly, viewed from the disk side;and

[0046]FIGS. 18A and 18B are schematic diagrams illustrating magneticstructures having edge domains.

DETAILED DESCRIPTION

[0047] Some embodiments of the invention will now be explained belowwith reference to the drawings.

[0048]FIG. 1 is a schematic diagram illustrating a cross-sectionalstructure of the substantial part of a magnetoresistive effect elementaccording to the first embodiment of the invention. Themagnetoresistance element 10 shown here has a ferromagnetic tunneljunction structure interposing an insulating film 2 between a magneticmulti-layered film 1 and a ferromagnetic film 3. The magneticmulti-layered film 1 has a ferromagnetic property as a whole, and itcorresponds to a simplex ferromagnetic film in a conventionalferromagnetic tunnel junction structure. With this magneticmulti-layered film 1, a current flows between the magnetic multi-layeredfilm 1 and the ferromagnetic film 3, tunneling through the insulatingfilm 2, and the junction contact value varies proportionally to thecosine of the relative angle of magnetization orientations of themagnetic multi-layered film 1 and the ferromagnetic film 3.

[0049] As explained later, in case of using the magnetoresistive effectelement 10 as a magnetic detector element, for example, the magneticmulti-layered film 1 may be used as the “magnetically free layer”, andthe ferromagnetic film 3 may be used as the “magnetically pinned layer”.When the element 10 is used as a magnetic memory element, the magneticmulti-layered film 1 may be used as the “recording layer”, and theferromagnetic film 3 as the “reference layer”.

[0050] In the first specific example of the invention, the ferromagneticmulti-layered film 1 of the ferromagnetic tunnel junction element 10 isin form of a multi-layered structure of ferromagnetic layer1A/anti-ferromagnetic layer 1B/ferromagnetic layer 1C. However, themulti-layered structure shown in FIG. 1 may be reversed in stackingorder. That is, the magnetic multi-layered film 1 may underlie theinsulating film 2 and the ferromagnetic film 3 may overlie theinsulating film 3.

[0051]FIG. 2 is a schematic diagram of a multi-layered structure of themagnetic multi-layered film 1. The inventor closely examined magneticproperties of this kind of multi-layered structures, and got his ownknowledge.

[0052] CO₉₀Fe₁₀ was used as the material of the ferromagnetic layers 1A,1C, and IrMn was used as the intervening anti-ferromagnetic layer 1B.The ferromagnetic layers 1A, 1C were 2 nm thick and 3 nm thick,respectively, and the anti-ferromagnetic layer 1B was 1 nm thick. Thismulti-layered film was sized 0.1 μm in width L and 0.3 μm in length L,and had a rectangular shape having the aspect ratio of 1:3.Additionally, the ferromagnetic layers 1A, 1C were assumed to be inexchange coupling of the magnitude as large as 30 Oe (oersted).

[0053]FIG. 3 is a graph diagram showing magnetic hysteresis of themagnetic multi-layered film 1 shown in FIG. 2. In the graph, magneticfield intensity applied is put on the abscissa, and ratio ofmagnetization relative to the saturation magnetization Ms is put on theordinate.

[0054] In FIG. 3, coercive force is defined as the intensity of themagnetic field corresponding to the width of the hysteresis curve. Inthe magnetic multi-layered film 1 shown in FIG. 2, interaction byexchange coupling of the anti-ferromagnetic layer 1B works to theferromagnetic layers 1A, 1C. Therefore, the plus side and the minus sideof the X-axis are different in coercive force. Thus these values ofcoercive force are herein called “right coercive force” (plus side) and“left coercive force” (minus side). In this specific example, exchangecoupling is not so large. Therefore, almost no difference between rightand left sides. The right coercive force is 229 Oe, and the leftcoercive force is 231 Oe.

[0055]FIG. 4 is a graph diagram showing magnetic hysteresis of a simplexferromagnetic layer taken as a comparative example. That is, here isshown the magnetic property of a simplex ferromagnetic layer and not ofa multi-layered structure interposing an anti-ferromagnetic layer asshown in FIG. 2.

[0056] In the hysteresis curve of FIG. 4, there is no shift as shown inthe hysteresis curve of FIG. 3 (labeled A and B in FIG. 3). The rightand left coercive forces are equally as high as 294 Oe, and it is higherthan of FIG. 3. That is, it is appreciated that the coercive force ofthe magnetic multi-layered film 1 shown in FIGS. 1 and 2 is lower thanthat of the simplex ferromagnetic layer.

[0057] Additionally, the embodiment of the invention is effective alsofor improving thermal stability of the magnetoresistive effect element.For example, as parameter indicating durability of a magnetic recordingmedium against thermal turbulence. the following equation can bedefined.

α=(KuV)/(k _(B) T)

[0058] where Ku is the magnetic anisotropy parameter, V is the volume,K_(B) is the Boltzmann constant, and T is the temperature.

[0059] In general, when the parameter α is in the range 60 through 80,the magnetic recording medium can be considered to be thermally stable.Since this parameter a depends upon the volume of the magnetic element,if the ferromagnetic layer becomes thicker, the value of α increases,and the thermal stability is enhanced. However, when the volume of themagnetic element increases, the coercive force also increases and makesinformation writing difficult. Therefore, a ferromagnetic layer having asmall coercive force and excellent thermal stability is requested as thefree layer.

[0060] The ferromagnetic multi-layered film 1 used in the embodiment ofthe invention is comprised of at least two ferromagnetic layers 1A, 1C,and the intervening anti-ferromagnetic layer 1B. Therefore, each of theferromagnetic layers 1A, 1C can be thinned to decrease the coerciveforce. On the other hand, since the ferromagnetic layers 1A, 1C arecoupled via the anti-ferromagnetic layer 1B, the volume of the magneticelement may be regarded to be the total of the ferromagnetic layers 1A,1C, and the value of the parameter α is therefore doubled. That is, theembodiment of the invention can provide a free layer satisfying both asmall coercive force and high thermal stability.

[0061] This effect of reducing the coercive force and improving thethermal stability is not limitative to the above-explained specificexample. For instance, as the material of the ferromagnetic layers 1A,1C, typical magnetic materials such as iron (Fe), cobalt (Co), nickel(Ni), their multi-layered structures and alloys are also usablesimilarly.

[0062] Magnetic amorphous alloys are also usable as the material of theferromagnetic layers 1A, 1C. More specifically, boron (B)-familyamorphous alloys such as FeB, CoB, CoNbB, CoFeB and NiFeB, phosphorus(P)-family amorphous alloys such as FeP and CoP, and zirconium(Zr)-family amorphous alloys such as FeZr, CoZr, NiZr and CoNbZr can beused.

[0063] Also, the material of the anti-ferromagnetic layer 1B can beselected from various kinds of anti-ferromagnetic materials includingmanganese-family antiferromagnetic materials such as platinum manganese(PtMn), iron manganese (FeMn), ruthenium manganese (RuMn), nickelmanganese (NiMn) and palladium platinum manganese (PdPtMn). Especially,high-conductivity materials are preferable.

[0064] Thickness of the anti-ferromagnetic layer 1B is preferablyadjusted to fall in the range not thinner than 0.1 nm and not exceeding50 nm so that moderate exchange coupling is obtained and the coerciveforce can be decreased.

[0065] The device size can be determined appropriately, depending uponits intended way of use. When the width is smaller than 1 μmapproximately, the coercive force is remarkably reduced as compared withthe simplex ferromagnetic layer. In regard to the aspect ratio, in casethe “edge domain” generates as explained with reference to FIGS. 18A and18B, especially remarkable effect is obtained. For example, when theaspect ratio is 1:1.5 through 1:10, a large effect is obtained.

[0066] Further, as explained in detail in Japanese Patent ApplicationNo. 2001-076614 in the name of the same Inventor, if a magnetoresistiveeffect element is shaped to be wider in its end portions than in itscentral portion when viewed in its plan view, it contributes tostabilization of the “edge domain” in its end portions and thereby makesit possible to further reduce the switching magnetic field, i.e. themagnetic field for writing. In this case, the ideal plan-view shape ofthe magnetoresistive effect element is a shape enlarged in width towardthe opposite end as a “bow tie”. If the “bow tie” shape is elongatedalong one of diagonal lines to degrade the symmetry, then the switchingmagnetic field can be reduced further.

[0067] On the other hand, thickness of the ferromagnetic layers 1A, 1Cis preferably not thicker than 10 nm and more preferably not thickerthan 5 nm.

[0068] Intensity of exchange coupling via the anti-ferromagnetic layer1B must be limited in a certain range such that the coercive force doesnot increase so much and the hysteresis does not shift so much from theorigin.

[0069]FIG. 5 is a graph diagram showing a relation between the exchangecoupling intensity Hex and the coercive force Hc. In FIG. 5, the solidline is the graph of the magnetic multi-layered film 1 shown in FIG. 2whereas the broken line is the graph of a simplex ferromagnetic layertaken as a comparative example.

[0070] It is appreciated from FIG. 5 that the coercive force Hc isconstantly 300 Oe in case of the simplex ferromagnetic layer. In case ofthe magnetic multi-layered film according to the embodiment of theinvention, the coercive force is minimum when the exchange couplingintensity Hex is nearly zero, and the coercive force Hc remainssufficiently small until Hex reaches approximately 300 Oe. When Hexfurther increases, the coercive force Hc increases. When Hex exceeds 1kOe, the coercive force exhibits a larger value than that of the simplexlayer (broken line).

[0071] Therefore, in order to reduce the reversal magnetization of themagnetic multi-layered film 1 in the magnetoresistive effect element,i.e. the switching magnetic field, intensity of the exchange couplingshould be limited below 1 kOe, more preferably below 400 Oe, and morepreferably 100 Oe.

[0072] Magnitude of the switching magnetic field of the magneticmulti-layered film 1 is smaller when two ferromagnetic layers 1A, 1B isequally 1.0 nm thick than when they are 2.0 nm thick and 3.0 nm thick,respectively. Therefore, the ferromagnetic layers 1A, 1B are preferablyadjusted to be thin, and advantageously limited below 3 nm.

[0073] The Inventor made a review on the magnetic structure (domainpattern) made by magnetization in the ferromagnetic layers 1A, 1C aswell.

[0074]FIG. 6A is a schematic diagram showing a domain pattern appearingin ferromagnetic layers 1A, 1C under exchange coupling of the magnitudeHc as large as 300e.

[0075] Apparently from FIG. 6A, magnetization of the ferromagneticlayers 1A, 1C is oriented substantially in one direction as a whole, andthe edge domains in the end portions do not occupy so large area.

[0076]FIG. 6B is a schematic diagram showing a domain pattern in asimplex ferromagnetic layer as a comparative example. In this case,magnetization different from that of the central portion appears in theend portions, and obvious “edge domains” are confirmed.

[0077] In general, since the TMR (tunneling magnetoresistance) effectdegrades under the existence of edge domains, edge domains had better besmall. The embodiment of the invention can sufficiently decrease thesize of edge domains as compared with that of a simplex ferromagneticlayer.

[0078] That is, when the magnetoresistive effect element according tothe embodiment is shaped to be wider in end portions than in the centralportion, “edge domains” in the end portions can be stabilized, and itcontributes to a more decrease of the switching magnetic field.

[0079] Next explained is the second specific example of the invention.

[0080]FIG. 7 is a schematic diagram showing a cross-sectional structureof the substantial part of a magnetoresistive effect element accordingto the second specific example of the invention.

[0081] Here again, the magnetoresistance element 10 has a ferromagnetictunnel junction structure in which the insulating film 2 is insertedbetween the magnetic multi-layered film 1′ and the ferromagnetic film 3.A current flows between the magnetic multi-layered film 1′ and theferromagnetic film 3, tunneling through the insulating film 2, and thejunction resistance value varies proportionally to the cosine of therelative angle between magnetization directions of the magneticmulti-layered film 1′ and the ferromagnetic film 3. As explained inconjunction with the first specific example, the magnetic multi-layeredfilm 1′ can be used as a “magnetically free layer” of a magneticdetector element or a “recording layer” of a magnetic memory.

[0082] The magnetic multi-layered film 1′ in this specific example isdifferent in configuration. That is, the magnetic multi-layered film 1′in this specific example includes nonmagnetic metal layers 1D, 1Ebetween the ferromagnetic layers 1A, 1C and the anti-ferromagnetic layer1B, respectively.

[0083] The nonmagnetic metal layers 1D, 1E have the role of moderatelyrelaxing magnetic coupling between the ferromagnetic layers 1A, 1C andthe anti-ferromagnetic layer 1B. Materials usable as the nonmagneticmetal layers 1D, 1E are, for example, copper (Cu), gold (Au), silver(Ag), rhenium (Re), osmium (Os), ruthenium (Ru), iridium (Ir), palladium(Pd), chromium (Cr), magnesium (Mg), aluminum (Al), rhodium (Rh) andplatinum (Pt). They are preferably thick enough to moderately alleviatethe magnetic coupling between the ferromagnetic layers 1A, 1C and theanti-ferromagnetic layer 1B.

[0084] More specifically, when the nonmagnetic metal layers 1D, 1E eachhave a thickness in the range not thinner than 0.1 nm and not thickerthan 10 nm, they can moderately relax the exchange coupling between theferromagnetic layers and the anti-ferromagnetic layer. If thenonmagnetic metal layers 1D, 1E are thicker, they will weaken theexchange coupling. If they are thinner, the function of relaxing theexchanging coupling will be insufficient.

[0085] The Inventor experimentally prepared the magnetic multi-layeredfilm 1′ according to this specific example and estimated its magneticproperties.

[0086] As the ferromagnetic layers 1A, 1C, Co₉₀Fe₁₀ or the multi-layeredstructure CO₉₀Fe₁₀/NiFe/CO₉₀Fe₁₀ was used. These two ferromagneticlayers 1A, 1C were equally 1.5 nm thick.

[0087] Even when using sputtering, material of the ferromagnetic layers1A, 1C is not limited to that of the specific example, and iron (Fe),cobalt (Co), nickel (Ni), and their multi-layered films or alloys arealso usable.

[0088] A layer 1B of iridium manganese (IrMn) as an anti-ferromagneticmaterial was formed between two ferromagnetic layers 1A, 1C. For thepurpose of appropriately controlling the exchanging interactionintensity working between the ferromagnetic layers 1A, 1C, compositionof IrMn was adjusted to limit the ratio of Ir outside the range from 22to 26 atomic %. This is attained by using IrMn containing 15 atomic % ofIr as the sputtering target, for example.

[0089] Alternatively, if a sputtering target containing Ir by a ratio inthe range from 22 to 26 atomic %, the composition ratio can be offsetfrom that range by simultaneously sputtering a metal target of Ir ormanganese (Mn). Alternatively, by adding an element other than iridiumand manganese, anti-ferromagnetism of IrMn may be suppressed. As theadditive element for this purpose, a nonmagnetic metal element such ascopper (Cu) or gold (Au), is preferably used.

[0090] Between the ferromagnetic layers 1A, 1C and the antiferromagneticlayer 1B, 0.8 nm thick copper (Cu) layers were provided as thenonmagnetic metal layers 1D, 1E. As these metal layers, however, variousother nonmagnetic metals such as gold (Au) and silver (Ag) are alsousable.

[0091] These films made by sputtering underwent fine processing to shapeit to be 0.5 μm in width and 1:4 in aspect ratio by using electron beamlithography. However, this specific example of these sizes does notlimit the scope of the invention.

[0092] With this multi-layered structure, magnetization characteristicswere measured.

[0093]FIG. 8A is a graph diagram showing magnetization and hysteresis ofthe multi-layered structure according to the second embodiment. Themagnetization curve shown here shows magnetization (ordinate) relativeto the applied magnetic field (abscissa).

[0094] In this specific example, a sputter target of IrMn containing Irby 22 atomic % was used for fabrication of the anti-ferromagnetic layer1B. Therefore, if the ferromagnetic layers 1A, 1C are placed adjacent tothe anti-ferromagnetic layer 1B, exchange coupling will becomeexcessively intensive.

[0095] In this specific example, however, intensity of the exchangecoupling can be controlled by inserting nonmagnetic metal layers 1D, 1E.More specifically, the coercive force of 5 Oe and the switching magneticfield of 35 Oe were obtained.

[0096]FIG. 8B is a graph diagram showing magnetization and hysteresis ina simplex ferromagnetic layer taken as a comparative example. Ascompared with FIG. 8A, the coercive force gradually increases to above300 Oe.

[0097] That is, in this specific example, by inserting the nonmagneticmetal layers 1D, 1E, it is possible to adequately adjust the exchangecoupling between the anti-ferromagnetic layer 1B and the ferromagneticlayers 1A, 1C and thereby reduce the coercive force of the entiremagnetic multi-layered films.

[0098] Next explained is a result of analysis of the scaling of theswitching magnetic field following microminiaturization in regard to themagnetoresistive effect element according to an embodiment of theinvention. By fine processing, width of the ferromagnetic layers 1A, 1Cwas adjusted to 0.2 μm, 0.5 μm, 0.8 μm and 1.2 μm, and their values ofcoercive force Hc were measured.

[0099]FIG. 9 is a graph diagram plotting values of coercive force inrelation to reciprocals of the width of the ferromagnetic layers 1A, 1C.That is, here are shown changes in coercive force in themagnetoresistive effect element according to the first specific exampleof the invention by black square dots, together with those of aconventional magnetic simplex film (made of Co₉₀Fe₁₀ and 3,0 nm thick)shown by x marks.

[0100] It is appreciated from FIG. 9 that coercive force, i.e. switchingmagnetic field, is smaller in the present invention for all values ofthe size width.

[0101] If the result obtained with the present invention is extended tothe width of 0.1 μm, the minimum switching magnetic field as small asapproximately 84 oersted (Oe) is obtained when a weak ferromagneticcoupling exists. In contrast, in case a simplex ferromagnetic layer asthe prior art is used, the switching magnetic field reaches 100 oersted(Oe) or more when the width is 0.5 μm, and at a still narrower width,the switching magnetic field rapidly increases. Apparently therefore,its practical application is difficult.

[0102] Additionally explained is a result of computer simulation toreview magnitudes of the magnetic field caused by a current wiringprovided in the magnetoresistive effect element. The current wiring hasa rectangular section 0.1 μm wide and having the aspect ratio of 1:2,and copper (Cu) or tungsten (W) is used as its material. All around thewiring, or around a part thereof, a shield of a material having a highmagnetic permeability such as nickel iron (NiFe) alloy is formed.

[0103] If the current of 5.8×10⁶ A/cm² is supplied to the wiring,magnitude of the magnetic field at a distance of 50 nm from the wiringbecomes approximately 90 oersted (Oe). Therefore, even in the case wherethe ferromagnetic layers 1A, 1C are 0.1 μm wide, magnetic reversal ispossible in the magnetoresistive effect element according to theembodiment of the invention. That is, if a magnetic memory element isfabricated by using the magnetoresistive effect element according to theembodiment, magnetic reversal, i.e. “writing”, is enabled by themagnetic field generated from the current wiring even when theferromagnetic layers 1A, 1C are miniaturized to the level around 0.1 μm.

[0104] Next explained is a magnetoresistive effect element taken as thethird specific example of the invention.

[0105]FIG. 10 is a diagram showing a cross-sectional structure of thesubstantial part of a magnetoresistive effect element taken as the thirdspecific example of the invention. In FIG. 10, some of componentsequivalent to those already explained in conjunction with FIGS. 1through 9 are labeled with common reference numerals, and their detailedexplanation is omitted.

[0106] Here again, the magnetoresistance element 10 has a ferromagnetictunnel junction structure in which the insulating film 2 is insertedbetween the magnetic multi-layered film 1″ and the ferromagnetic film 3.A current flows between the magnetic multi-layered film 1″ and theferromagnetic film 3, tunneling through the insulating film 2, and thejunction resistance value varies proportionally to the cosine of therelative angle between magnetization directions of the magneticmulti-layered film 1″ and the ferromagnetic film 3. As explained inconjunction with the first specific example, the magnetic multi-layeredfilm 1′ can be used as a “magnetically free layer” of a magneticdetector element or a “recording layer” of a magnetic memory.

[0107] The magnetic multi-layered film 1″ in this specific example isdifferent in configuration. That is, the magnetic multi-layered film 1″in this specific example includes dielectric layers 1F, 1G between theferromagnetic layers 1A, 1C and the anti-ferromagnetic layer 1B,respectively.

[0108] The dielectric layers 1F, 1G have the role of moderately relaxingmagnetic coupling between the ferromagnetic layers 1A, 1C and theanti-ferromagnetic layer 1B. Materials usable as the dielectric layers1F, 1G are, for example, oxides or nitrides of various kinds of elementsincluding silicon (Si), aluminum (Al), tantalum (Ta) and others.

[0109] The dielectric layers 1F, 1G are preferably thick enough tomoderately alleviate the magnetic coupling between the ferromagneticlayers 1A, 1C and the anti-ferromagnetic layer 1B.

[0110] More specifically, when the dielectric layers 1F, 1G each have athickness in the range not thinner than 0.1 nm and not thicker than 10nm, they can moderately relax the exchange coupling between theferromagnetic layers and the anti-ferromagnetic layer. If thenonmagnetic metal layers 1D, 1E are thicker, they will weaken theexchange coupling. If they are thinner, the function of relaxing theexchanging coupling will be insufficient.

[0111] Insertion of the dielectric layers 1F, 1G ensures the same effectas that of the second specific example. That is, by inserting thedielectric layers 1F, 1G, it is possible to adequately adjust theexchange coupling between the anti-ferromagnetic layer 1B and theferromagnetic layers 1A, 1C and to reduce the coercive force of theentire magnetic multi-layered film.

[0112] Next explained is a magnetoresistive effect element taken as thefourth specific example of the invention.

[0113]FIG. 11A is a diagram showing a cross-sectional structure of thesubstantial part of a magnetoresistive effect element taken as thefourth specific example of the invention. In FIG. 11A, some ofcomponents equivalent to those already explained in conjunction withFIGS. 1 through 10 are labeled with common reference numerals, and theirdetailed explanation is omitted.

[0114] The magnetoresistive effect element 10 shown here has a so-called“double-junction structure” including two ferromagnetic tunnel junctionstructures, each of which includes a ferromagnetic film 3 and anintervening insulating film 2, provided at both side of the magneticmulti-layered film 1. In each ferromagnetic tunnel junction structure, acurrent flows between the magnetic multi-layered film 1 and theferromagnetic film 3, tunneling through the insulating film 3, and thejunction resistance value varies proportionally to the cosine of therelative angle between magnetization directions of the magneticmulti-layered film 1 and the ferromagnetic film 3. As explained inconjunction with the first specific example, the magnetic multi-layeredfilm 1 can be used as a “magnetically free layer” of a magnetic detectorelement or a “recording layer” of a magnetic memory.

[0115] The use of this double-junction structure contributes to increasethe output voltage as well as the current variable ratio and enableshigher-sensitivity magnetic detection and realization of a memoryelement excellent in write and read property.

[0116] In this fourth specific example, the magnetic multi-layered film1′ already explained in conjunction with FIG. 7 or the magneticmulti-layered film 1″ already explained in conjunction with FIG. 10 maybe employed instead of the film 1 as well.

[0117] Next explained is a magnetoresistive effect element taken as thefifth specific example of the invention.

[0118]FIG. 11B is a diagram showing a cross-sectional structure of thesubstantial part of a magnetoresistive effect element taken as the fifthspecific example of the invention. In FIG. 11B, some of componentsequivalent to those already explained in conjunction with FIGS. 1through 11A are labeled with common reference numerals, and theirdetailed explanation is omitted.

[0119] The magnetoresistive effect element 10 shown here has a so-called“multi-junction structure” including two magnetic multi-layered films 1(1′, 1″) and two ferromagnetic films 3. Between each magneticmulti-layered film 1 (1′, 1″) and each ferromagnetic film 3, aferromagnetic tunnel junction structure with an intervening insulatingfilm 2 is provided. In each ferromagnetic tunnel junction structure, acurrent flows between the magnetic multi-layered film 1(1′, 1″) and theferromagnetic film 3, tunneling through the insulating film 3, and thejunction resistance value varies proportionally to the cosine of therelative angle between magnetization directions of the magneticmulti-layered film 1 (1′, 1″) and the ferromagnetic film 3. As explainedin conjunction with the first specific example, the magneticmulti-layered film 1(1′, 1″) can be used as a “magnetically free layer”of a magnetic detector element or a “recording layer” of a magneticmemory.

[0120] Between those two ferromagnetic tunnel junction structures, ananti-ferromagnetic film 4 is inserted. That is, the antiferromagneticfilm 4 is inserted between two magnetic multi-layered films 1(1′, 1″).

[0121] The use of this multi-junction structure contributes to increasethe output voltage as well as the current variable ratio and enableshigher-sensitivity magnetic detection and realization of a memoryelement excellent in write and read property.

[0122] Additionally, the magnetoresistive effect element according tothe invention is not limited to the example of FIG. 11B, but may bemodified to other types of multi-junction magnetoresistive effectelements by combining three or more ferromagnetic tunnel junctionstructures, for example.

[0123] Next explained is a specific example that is an application ofthe magnetoresistive effect element according to an embodiment of theinvention to cells of a magnetic random access memory.

[0124] In case a magnetoresistive effect element according to anyembodiment of the invention is used as a magnetic memory element,because of a sufficiently small switching magnetic field, quick andreliable writing is ensured by using the magnetic memory element as acell of a large-capacity magnetic random access memory (MRAM).

[0125]FIG. 12 is a schematic diagram illustrating configuration of thesubstantial part of a MRAM according to an embodiment of the invention.

[0126] In MRAM shown here, one end of the magnetoresistive effectelement (TMR) 10 according to an embodiment of the invention isconnected to a bit line 20, and the other end is connected to aswitching element 40 such as MOSFET via a wiring 30. In FIG. 12, the bitline 20 extends substantially in parallel to the sheet plane.

[0127] MOSFET 40 includes a source 44 and a drain 46 formed in asemiconductor layer, and can be controlled to turn ON and OFF by avoltage applied to a gate 42.

[0128] In addition to them, a writing word line 50 is formed to extendperpendicularly to the bit line 20. In FIG. 12, the word line 50 extendssubstantially vertically to the sheet plane. The magnetoresistive effectelement 10 is positioned near the crossing point of the bit line 20 andthe word line 50.

[0129] In the magnetoresistive effect element 10, any one of themagnetic multi-layered films 1, 1′, 1″ already explained in conjunctionwith FIGS. 1 through 11 functions as the “recording layer”, and theferromagnetic film 3 opposed to the magnetic multi-layered film via theinsulating film 2 functions as a “pinned layer”. Thus a tunnelingcurrent flows through the insulating film.

[0130] A number of such cells are integrated in an array to make up arandom access memory. The switching element 40 is provided to selectdesired one of these cells. As the switching element 40, a diode or anyother appropriate element having the switching function may be used inlieu of MOSFET. That is, it is also acceptable to stack a diode and themagnetoresistive effect element according to the invention, connect thebit line 20 on the magnetoresistive effect element, and integrate anumber of such cells in an array.

[0131] Operations of the cell shown in FIG. 12 are explained here. Forreading data, MOSFET 40 us turned ON by applying a predetermined voltageto the gate 40, and a sense current is supplied to the magnetoresistiveeffect element 10 via the bit line 20.

[0132] For writing, MOSFET 40 is turned OFF, and a write current issupplied to the bit line 20 and the word line 50 respectively. Then, amagnetic field corresponding to the current is generated in each ofthem. Thus the total magnetic field obtained at the crossing point ofthe bit line 20 and the word line 50 inverts the magnetic field in therecording layer in the cell at that position. In this case, bycontrolling the flowing direction of the current to the bit line 20 andthe word line 50 and thereby reversing the magnetic field, one of twovalues can be stored as information as desired.

[0133] As an alternative method for writing, it is also possible to turnON the MOSFET 40 and supply a write current to the magnetoresistiveeffect element 10 through the bit line 20. In this case, the word line50 may be omitted.

[0134] With this specific example, the coercive force can be maintainedlow even when the device size is miniaturized, by using appropriate oneof magnetic multi-layered films 1, 1′, 1″ explained with reference toFIGS. 1 through 11 as the recording layer. That is, the specific exampleensures the effect of facilitating writing in the “recording layer”.

[0135] That is, the embodiment of the invention enables reliable, easywriting even with more miniaturized elements, and can thereby realize anintegrated-type magnetic memory by a much higher density thanconventional ones.

[0136]FIG. 13 is a cross-sectional view showing another specific exampleof MRAM cell according to an embodiment of the invention;

[0137] MRAM shown here has a structure using no switching transistor inthe memory cell.

[0138] One end of the magnetoresistive (TMR) element 10 according to theembodiment of the invention is connected to the bit line 20, and theother end thereof is connected to the word line 50. The bit line 20 andthe word line 50 extend to intersect with each other substantially at aright angle. That is, in FIG. 13, the bit line 20 extends substantiallyin parallel to the sheet plane, and the word line 50 extendssubstantially vertically to the sheet plane. The magnetoresistive effectelement 10 is positioned near the crossing point of the bit line 20 andthe word line 50.

[0139] In the magnetoresistive effect element 10, any one of themagnetic multi-layered films 1, 1′, 1″ already explained in conjunctionwith FIGS. 1 through 11 functions as the “recording layer”, and theferromagnetic film 3 opposed to the magnetic multi-layered film via theinsulating film 2 functions as a “pinned layer”. Thus a tunnelingcurrent flows through the insulating film. A number of such cells areintegrated in an array to make up a random access memory.

[0140] Operations of the cell shown in FIG. 13 are explained here. Firstin reading operation, by selecting a predetermined bit line 20 and apredetermined word line 50, and supplying a sense current to themagnetoresistive effect element 10 connected to their crossing point,data can be read.

[0141] In writing operation, a write current is supplied to apredetermined bit line 20 and a writing word line 55. As a result, amagnetic field corresponding to the current is generated in each ofthem. Thus the total magnetic field obtained at the crossing point ofthe bit line 20 and the writing word line 55 inverts the magnetic fieldin the recording layer in the cell at that position. In this case, bycontrolling the flowing direction of the current to the bit line 20 andthe writing word line 55 and thereby reversing the magnetic field, oneof two values can be stored as information as desired.

[0142] Also with this specific example, the coercive force can bemaintained low even when the device size is miniaturized, by usingappropriate one of magnetic multi-layered films 1, 1′, 1″ explained withreference to FIGS. 1 through 11 as the recording layer. That is, thespecific example ensures the effect of facilitating writing in the“recording layer”.

[0143] Besides, as this specific example does not require any switchingtransistor, it becomes quite easy to stack the memory cells in thevertical direction. By employing such a stacked configuration, amagnetic memory with a much larger capacity can be easily realizedwithout increasing a chip size.

[0144] Next explained is an embodiment that is an application of themagnetoresistive effect element according to an embodiment of theinvention to a magnetic head.

[0145]FIGS. 14 and 15 are diagrams schematically showing configurationof the substantial part of a magnetic head according to an embodiment ofthe invention. FIG. 14 is a cross-sectional view of themagnetoresistance element, taken along a plane substantially in parallelto the medium-facing plane P opposed to a magnetic recording medium (notshown). FIG. 15 is a cross-sectional view of the magnetoresistanceelement, taken along a plane vertical to the medium-facing plane P.

[0146] A lower electrode 70 and an upper electrode 60 are provided onand under the magnetoresistive effect element 10 according to theembodiment already explained with reference to FIGS. 1 through 9, and ininsulating film 90 is formed on opposite side surfaces of themagnetoresistive effect element 10 in FIG. 14. Additionally, as shown inFIG. 2, the insulating film 90 is formed on the back surface of themagnetoresistive effect element 10 as well.

[0147] A sense current to the magnetoresistive effect element 10 issupplied vertically to the film plane of the multi-layered film by theoverlying and underlying electrodes 60, 70.

[0148] According to this embodiment of the invention, the use of themagnetic multi-layered film 1, 1′ as the magnetically free layer of themagnetoresistance element 10 contributes to suppress reversalmagnetization even in microminiaturized elements. Therefore, even withan ultrahigh-density magnetic recording system using microminiaturizedmagnetoresistive effect elements, highly sensitive magnetic reproductionis possible.

[0149] Next explained is a magnetic recording/reproducing apparatusaccording to the invention. The magnetic head using the magnetoresistiveeffect element according to the invention, as explained with referenceto FIGS. 1 through 15, can be incorporated in a magnetic head assemblyof a recording/reproducing integral type, for example, and can bemounted in a magnetic reproducing apparatus.

[0150]FIG. 16 is a perspective view that schematically shows aconfiguration of a major part of a magnetic recording/reproducingapparatus according to the embodiment of the invention. The magneticrecording/reproducing apparatus 150 according to the invention is anapparatus of a type using a rotary actuator. In FIG. 16, a recordingmagnetic disk 200 is mounted on a spindle 152 and rotated in the arrow Adirection by a motor, not shown, which is responsive to a control signalfrom a drive device controller, not shown. The magnetic recordingapparatus according to the embodiment of the invention may also includea plurality of recording magnetic disks 200.

[0151] A head slider 153 executed recording or reproduction ofinformation to be stored in the magnetic disk 200 is attached to the tipof a thin-film suspension 154. The head slider 153 includes the magnetichead according to the foregoing embodiment near its tip.

[0152] When the magnetic disk 200 rotates, the medium-facing surface(ABS) of the head slider 153 is held with a predetermined floatingamount from the surface of the magnetic disk 200. Alternatively, theapparatus may employ a contact-type configuration where the slider 153is in contact with the disk 200 during the operation

[0153] The suspension 154 is connected to one end of an actuator arm 155that has a bobbin portion for holding a drive coil, not shown. At theother end of the actuator arm 155, a voice coil motor 156, which is akind of linear motor, is provided. The voice coil motor 156 is composedof a drive coil, not shown, wound up on the bobbin portion of theactuator arm 155, and a magnetic circuit made up of a permanent magnetand an opposed yoke disposed in confrontation so as to sandwich thedrive coil.

[0154] The actuator arm 155 is held by ball bearings, not shown, whichare provided upper and lower two positions of a rigid shaft 157 for freerotational and slidable movements with a driving force from the voicecoil motor 156.

[0155]FIG. 17 is an enlarged, perspective view of the magnetic headassembly from the actuator arm 155 to its distal end, taken from thedisk side. The magnetic head assembly 160 includes the actuator arm 155having the bobbin portion for holding the drive coil, for example, andthe suspension 154 is connected to one end of the actuator arm 155.

[0156] At the extremity of the suspension 154, the head slider 153incorporating the reproducing magnetic head which includes amagnetoresistive effect element according to the invention is attached.A recording head may be combined with it. The suspension 154 has a leadline 164 for writing and reading signals, and the lead line 164 andelectrodes of the magnetic head incorporated in the head slider 153 areelectrically connected. Numeral 165 denotes an electrode pad of themagnetic head assembly 160.

[0157] The magnetic recording/reproducing apparatus according to theinvention, as shown in FIGS. 16 and 17, can greatly improve therecording density as compared with conventional systems, and cansimultaneously improve the stability and reliability of reproducedsignals.

[0158] Heretofore, embodiments of the invention have been explained indetail with reference to some specific examples. The invention, however,is not limited to these specific examples.

[0159] For example, material, shape and thickness of the ferromagneticlayer, anti-ferromagnetic layer, insulating film and ferromagnetic filmof the magnetoresistive effect element according to the invention may beappropriately selected by those skilled in the art within the knowntechniques to carry out the invention as taught in the specification andobtain equivalent effects.

[0160] Further, also concerning the magnetic memory and the magnetichead according to the invention, those skilled in the art will be ableto carry out the invention by appropriately selecting a material or astructure within the known techniques.

[0161] It will be also appreciated that the invention is applicable notonly to magnetic heads or magnetic reproducing apparatuses of thelengthwise recording type but also to those of the perpendicularmagnetic recording type and ensures substantially the same effects.

[0162] The magnetic reproducing apparatus according to the embodiment ofthe invention may be of a so-called stationary type incorporating aparticular recording medium in a stationary fashion, or of a so-called“removable” type permitting recording mediums to be loaded and unloaded.

[0163] As explained above, embodiments of the invention can providemagnetoresistive effect elements low in coercive force and thereforesmall in switching magnetic field.

[0164] That is, according to embodiments of the invention, it ispossible to provide a tunnel junction magnetoresistive effect elementincluding a magnetic multi-layered film, ferromagnetic film andintervening insulating film such that a current flows between themagnetic multi-layered film and the ferromagnetic film, tunnelingthrough the insulating film, in which the magnetic multi-layered filmincludes a first ferromagnetic layer, second ferromagnetic layer andanti-ferromagnetic layer inserted between the first and secondferromagnetic layers. In the magnetoresistive effect element having suchconfiguration, the coercive force is small, and the switching magneticfield is small accordingly.

[0165] Further, when the magnetoresistive effect element according tothe embodiment is shaped to be wider in end portions than in the centralportion, “edge domains” in the end portions can be stabilized, and itcontributes to a more decrease of the switching magnetic field.

[0166] On the other hand, in case the magnetoresistive effect element isused as a memory cell of a magnetic memory, the wrote current suppliedfor generating a magnetic field necessary for magnetic reversal may besmaller. Therefore, the magnetic memory using the elements according tothe invention as its memory cells consumes less power and can be denselyintegrated. Additionally, it is enhanced in switching speed as well.

[0167] In case the magnetoresistive effect element according to anembodiment of the invention is used as a magnetic detector element forreproduction in a magnetic recording system, high reproducingsensitivity is ensured even when the detector element is miniaturized inaccordance with the requirement of higher recording densities, and amagnetic recording system having ultrahigh recording density can berealized.

[0168] As such, the invention greatly contributes to realization of ahigh-integrated magnetic memory using magnetoresistive effect elementsand an ultrahigh-density magnetic recording system, which must be agreat industrial advantage.

[0169] While the present invention has been disclosed in terms of theembodiment in order to facilitate better understanding thereof, itshould be appreciated that the invention can be embodied in various wayswithout departing from the principle of the invention. Therefore, theinvention should be understood to include all possible embodiments andmodification to the shown embodiments which can be embodied withoutdeparting from the principle of the invention as set forth in theappended claims.

What is claimed is:
 1. A magnetoresistive effect element comprising: afirst magnetic multi-layered film; a first ferromagnetic film; and afirst insulating film interposed between said first magneticmulti-layered film and said first ferromagnetic film, a current flowingbetween said first magnetic multi-layered film and said firstferromagnetic film by tunneling through said first insulating film, andsaid first magnetic multi-layered film including a first ferromagneticlayer, a second ferromagnetic layer and a first antiferromagnetic layerinterposed between said first and second ferromagnetic layers.
 2. Amagnetoresistive effect element according to claim 1, wherein magnitudeof exchange coupling which acts between said first ferromagnetic layerand said first anti-ferromagnetic layer is limited not to exceed 1000oersted, and magnitude of exchange coupling which acts between saidsecond ferromagnetic layer and said first anti-ferromagnetic layer islimited not to exceed 1000 oersted.
 3. A magnetoresistive effect elementaccording to claim 1, wherein said first anti-ferromagnetic layer ismade of an alloy selected from the group consisting of iridium manganese(IrMn), platinum manganese (PtMn), iron manganese (FeMn), rutheniummanganese (RuMn), nickel manganese (NiMn), and palladium platinummanganese (PdPtMn), and thickness of said first anti-ferromagnetic layeris in the range not thinner than 0.1 nm and not thicker than 50 nm.
 4. Amagnetoresistive effect element according to claim 1, which is shaped tobe wider in end portions than in a central portion.
 5. Amagnetoresistive effect element according to claim 1, wherein said firstmagnetic multi-layered film further includes: a first nonmagnetic metallayer interposed between said first ferromagnetic layer and said firstanti-ferromagnetic layer; and a second nonmagnetic metal layerinterposed between said second ferromagnetic layer and said firstanti-ferromagnetic layer.
 6. A magnetoresistive effect element accordingto claim 5, wherein thicknesses of said first and second nonmagneticmetal layers are in the range not thinner than 0.1 nm and not thickerthan 10 nm.
 7. A magnetoresistive effect element according to claim 5,wherein magnitude of exchange coupling which acts between said firstferromagnetic layer and said first anti-ferromagnetic layer is limitednot to exceed 1000 oersted, and magnitude of exchange coupling whichacts between said second ferromagnetic layer and said firstanti-ferromagnetic layer is limited not to exceed 1000 oersted.
 8. Amagnetoresistive effect element according to claim 5, wherein said firstanti-ferromagnetic layer is made of an alloy selected from the groupconsisting of iridium manganese (IrMn), platinum manganese (PtMn), ironmanganese (FeMn), ruthenium manganese (RuMn), nickel manganese (NiMn),and palladium platinum manganese (PdPtMn), and thickness of said firstanti-ferromagnetic layer is in the range not thinner than 0.1 nm and notthicker than 50 nm.
 9. A magnetoresistive effect element according toclaim 5, which is shaped to be wider in end portions than in a centralportion.
 10. A magnetoresistive effect element according to claim 1,wherein said first magnetic multi-layered film further includes: a firstdielectric layer interposed between said first ferromagnetic layer andsaid first anti-ferromagnetic layer; and a second dielectric layerinterposed between said second ferromagnetic layer and said firstanti-ferromagnetic layer.
 11. A magnetoresistive effect elementaccording to claim 10, wherein thicknesses of said first and seconddielectric layers are in the range not thinner than 0.1 nm and notthicker than 10 nm.
 12. A magnetoresistive effect element according toclaim 10, wherein magnitude of exchange coupling which acts between saidfirst ferromagnetic layer and said first anti-ferromagnetic layer islimited not to exceed 1000 oersted, and magnitude of exchange couplingwhich acts between said second ferromagnetic layer and said firstanti-ferromagnetic layer is limited not to exceed 1000 oersted.
 13. Amagnetoresistive effect element according to claim 10, wherein saidfirst anti-ferromagnetic layer is made of an alloy selected from thegroup consisting of iridium manganese (IrMn), platinum manganese (PtMn),iron manganese (FeMn), ruthenium manganese (RuMn), nickel manganese(NiMn), and palladium platinum manganese (PdPtMn), and thickness of saidfirst anti-ferromagnetic layer is in the range not thinner than 0.1 nmand not thicker than 50 nm.
 14. A magnetoresistive effect elementaccording to claim 10, which is shaped to be wider in end portions thanin a central portion.
 15. A magnetoresistive effect element according toclaim 1, further comprising: a second ferromagnetic film; and a secondinsulating film interposed between said first magnetic multi-layeredfilm and said second ferromagnetic film, a current flowing through saidfirst magnetic multi-layered film and said first and secondferromagnetic films by tunneling through said first and secondinsulating films.
 16. A magnetoresistive effect element according toclaim 1, further comprising: a second magnetic multi-layered film; asecond ferromagnetic film; and a second insulating film interposedbetween said second magnetic multi-layered film and said secondferromagnetic film, a current flowing through said first and secondmagnetic multi-layered films and said first and second ferromagneticfilms by tunneling through said first and second insulating films, andsaid second magnetic multi-layered film including a third ferromagneticlayer, a fourth ferromagnetic layer and a second antiferromagnetic layerinterposed between said third and fourth ferromagnetic layers.
 17. Amagnetoresistive effect element according to claim 16, wherein magnitudeof exchange coupling which acts between said first ferromagnetic layerand said first anti-ferromagnetic layer is limited not to exceed 1000oersted, magnitude of exchange coupling which acts between said secondferromagnetic layer and said first anti-ferromagnetic layer is limitednot to exceed 1000 oersted, magnitude of exchange coupling which actsbetween said third ferromagnetic layer and said secondanti-ferromagnetic layer is limited not to exceed 1000 oersted, andmagnitude of exchange coupling which acts between said fourthferromagnetic layer and said second anti-ferromagnetic layer is limitednot to exceed 1000 oersted.
 18. A magnetoresistive effect elementaccording to claim 16, wherein said first and second anti-ferromagneticlayers are made of an alloy selected from the group consisting ofiridium manganese (IrMn), platinum manganese (PtMn), iron manganese(FeMn), ruthenium manganese (RuMn), nickel manganese (NiMn), andpalladium platinum manganese (PdPtMn), and thicknesses of said first andsecond anti-ferromagnetic layers are in the range not thinner than 0.1nm and not thicker than 50 nm.
 19. A magnetic memory comprising amagnetoresistive effect element including: a first magneticmulti-layered film; a first ferromagnetic film; and a first insulatingfilm interposed between said first magnetic multi-layered film and saidfirst ferromagnetic film, a current flowing between said first magneticmulti-layered film and said first ferromagnetic film by tunnelingthrough said first insulating film, said first magnetic multi-layeredfilm including a first ferromagnetic layer, a second ferromagnetic layerand a first antiferromagnetic layer interposed between said first andsecond ferromagnetic layers, said first ferromagnetic film of saidmagnetoresistive effect element being fixed in magnetizationorientation, and magnetization orientation of the entirety of saidferromagnetic multi-layered film being able to be re-written.
 20. Amagnetic memory comprising a magnetoresistive effect element, and awriting current wiring, said magnetoresistive effect element including:a first magnetic multi-layered film; a first ferromagnetic film; and afirst insulating film interposed between said first magneticmulti-layered film and said first ferromagnetic film, a current flowingbetween said first magnetic multi-layered film and said firstferromagnetic film by tunneling through said first insulating film, saidfirst magnetic multi-layered film including a first ferromagnetic layer,a second ferromagnetic layer and a first antiferromagnetic layerinterposed between said first and second ferromagnetic layers, saidfirst ferromagnetic film of said magnetoresistive effect element beingfixed in magnetization orientation, and magnetization orientation of theentirety of said ferromagnetic multi-layered film being able to bere-written by a magnetic field generated by a current supplied to saidwriting current wiring.
 21. A magnetic head comprising amagnetoresistive effect element including: a first magneticmulti-layered film; a first ferromagnetic film; and a first insulatingfilm interposed between said first magnetic multi-layered film and saidfirst ferromagnetic film, a current flowing between said first magneticmulti-layered film and said first ferromagnetic film by tunnelingthrough said first insulating film, and said first magneticmulti-layered film including a first ferromagnetic layer, a secondferromagnetic layer and a first anti-ferromagnetic layer interposedbetween said first and second ferromagnetic layers.